Smithy GN1300 - Manual (Page 94)

9. Install the chuck and check the cam rotation. Repeat as necessary.
Since there are three studs and cam mounts on the chuck, there are three possible
position that the chuck may be mounted. You will find that one of these positions will be
slightly more accurate than the others. Try the chuck in all three possible positions. Once
the most accurate position is determined, mark the chuck and spindle flange so that the
chuck can be installed in the same position each time that it is mounted onto the
machine. This is best done by putting a punch mark on the chuck and a corresponding
mark on the spindle flange.
This next step is only for the 3-jaw self centering chuck.
Mark each of the three jaws, and the slot it is in. Remove the jaws, and keeping them
in the same order, reinsert them into the next slot over making sure the scroll plate
engages the first thread on the first jaw. Try the jaws in all three positions; one should
be more accurate than the other two.
Leadscrew
Having trouble on the leadscrew backlash particularly on engaging the half
nut?
Leadscrew Backlash Adjustment
Excessive backlash in the longitudinal feed can come from two places:
1. The fit of the longitudinal feed screw to the right hand mounting trestle.
2. The fit of the half nut to the feed screw.
Screw to mount backlash
Engage the half nut lever. Slowly turn the longitudinal feed screw clockwise as viewed
from the right end of the machine and watch the gap between the dial and the feed screw
mounting trestle. Reverse the direction you are turning the feed screw and see if the gap
increases slightly. If so then there is some play in the mounting. To reduce the play,
accomplish the following.
1. Remove the bolt/ washer from the right end of the longitudinal feed screw.
2. Unscrew the handle from the end of the feed screw.
3. Using a punch and a small hammer, tighten the spanner nut about one eigth of a turn
and recheck the play in the screw.
4. If the play is acceptable, replace the handle and retaining bolt. If more adjustment is
needed, repeat the step above.
12: Troubleshooting
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